In accordance with a rapid spread of information relevant apparatuses and communication apparatuses such as a personal computer, a video camera and a portable telephone in recent years, the development of a battery to be utilized as a power source thereof has been emphasized. The development of a high-output and high-capacity battery for an electric automobile or a hybrid automobile has been advanced also in the automobile industry. A lithium battery has been presently noticed from the viewpoint of a high energy density among various kinds of batteries.
In the field of such a lithium battery, the intention of improving the performance of the battery is attempted while noticing an interface between an active material and an electrolyte material. For example, in Patent Literature 1, it is disclosed that the cathode active material surface of an all solid lithium battery is coated with a lithium ion conductive oxide to restrain a high-resistance layer from being formed at an interface between the cathode active material and a sulfide solid electrolyte.
On the other hand, for example, various methods are known as a method for producing composite particles such as a cathode active material whose surface is coated with the above-mentioned lithium ion conductive oxide. For example, in Patent Literature 2, it is disclosed that an active material and carbon are mixed by a mechano-fusion method and subjected to electrification sintering to produce electrode composite powder with high electrical conductivity; in Patent Literature 3, a method for producing composite particles with an average particle diameter of 5 to 200 μm, containing microparticles with an average particle diameter of 500 nm or less, is disclosed.